1. Field of the Invention
This invention relates to a dragline and, more particularly, to an improved method and apparatus for machining and assembling the tub and deck portions of the dragline.
2. Description of the Prior Art
In dragline structures and, in particular, walking draglines, the tremendous weights and loads transmitted by the deck to the tub pass through the deck rail, the flanged dolly wheels to the tub rail with the turning forces for the deck being transmitted to the gear on the tub flange. Slight or minor variations from a plane by the rolling surfaces of the tub rail or deck rail will cause galling or like problems between the rails and the dolly wheels leading to premature failure of the turning maneuverability of the deck relative to the tub. As a result, manufacturers of draglines have been forced to provide complex and time-consuming practices in an effort to assure that the rolling surfaces of the tub rail and deck rail are as close to a perfect plane as is possible to eliminate the galling problem.
Heretofore, complex systems have been and are being used to produce the planar surfaces on the rails. These systems consume as many as 1600 hours of expensive time, labor and equipment to produce the desired surface.
One such system entailed mounting a chain drive on the outside of the flanged girder to which a dolly is drivingly connected by an elongate chain and sprocket which supports a milling tool to mill the surface on the flange. The milling tool is a one-bit tool which subscribes advancing circular cuts as it advances around the flange. The key to the system is maintaining the chain and dolly in a plane.